1. Field of the Invention
The invention generally relates to a circuit board and a manufacturing method thereof, and more particularly, to a circuit board and a manufacturing method thereof which increases the adhesive strength between the copper layer and the dielectric layer in a modified semi-additive process (MSAP) through active particles in the dielectric layer.
2. Description of Related Art
In recent years, along with the staggering advancements of electronic technology, the high-tech electronics industries have come out one after another, so that electronic products with more humanized features and powerful functions are ceaselessly upgraded and developed towards the light, slim, short, small design tendency. In these electronic products, usually circuit boards with conductive traces are employed and disposed.
In order to increase the wiring density in a circuit board, a subtractive process is used to fabricate the circuit layer with line width of more than 40 μm in the circuit board. However, for line width of less than 40 μm, the subtractive process used to fabricate the circuit layer would reduce the product yield. Therefore, a semi-additive process (SAP) or a modified semi-additive process (MSAP) is used currently for fabricating the circuit layer with line width of less than 40 μm.
However, for a copper-clad laminate (CCL) used in an MSAP, the copper layer thereof is formed by laminating an ultra-thin copper foil with thickness of 3 μm with a dielectric substrate. Since the ultra-thin copper foil is quite thin and usually has low roughness (centreline arithmetic average roughness Ra and 10-point average roughness Rz), the adhesive strength between the circuit layer and the dielectric layer is poor. If making the copper foil further thinner, even the copper layer may be peeled from the dielectric substrate during the fabricating process, which reduces the reliability of the circuit board.